These inventions relate generally to turbines and have particular application to air turbine starters and to valves used in such starters. Such devices can be used, for example, in starting systems for gas turbine engines commonly found on aircraft.
An air turbine starter (xe2x80x9cATSxe2x80x9d) is a device used to start a turbine engine, such as a gas turbine jet engine. The air turbine starter is used to start the jet engine, much as a starter for an automobile is used to start the automobile""s engine. In order to start the jet engine, the air turbine starter is activated. The developer of the present inventions, Honeywell International, Inc., has for years successfully designed, developed and manufactured air turbine starters.
Air turbine starters A (FIG. 9) are typically mounted to the jet engine B through a gearbox C or other transmission assembly with a cover plate or wall D between the starter housing and the gearbox housing. The transmission transfers power from the starter to the jet engine to assist in starting jet engine. The transmission may also transmit power from the jet engine to other components linked to the transmission.
Some air turbine starters are lubricated in part using an assisted wet cavity design (AWC). In such a design, the turbine starter housing includes a mounting face or mounting flange which sealingly engages the gearbox, joining in such a way as to define a porting system, which allows free transfer of lubricating oil and air between the gearbox and starter. The oil port is in fluid communication with internal passages within the starter housing for distribution of the lubricating oil it has acquired. The air passage prevents a vapor lock that would prevent oil transfer. The oil port is located such that it acts as a sump passage or oil return passage and allows free flow of the oil between the starter and the gearbox.
Air flow between air turbine starters and the gearboxes to which they are attached is generally unrestricted. The gearbox and air turbine starter are typically pressurized two to four psi above atmospheric pressure. Generally, air turbine starters are very safe and reliable. However, under certain circumstances, the starter housing may be inadvertently punctured from the outside or from the inside. Under this type of failure mode, air will flow from the pressurized starter gearbox, through the puncture to the nacelle which is at two to four psi lower pressure. Because the air from the gearbox includes a substantial amount of oil entrained within it, this may result in reduced oil in the gearbox. If the air flow out of the gearbox and out of the starter is large enough, there may be enough oil loss from the gearbox to cause an unplanned engine shutdown.
Preferably, the starter and gearbox can exchange fluid under normal operations, and limit or control fluid flow from the starter and gearbox to the nacelle under failure conditions that result in a wall puncture. Thus, there is a need for an improved air turbine starter with fluid flow control. The present inventions fulfill this need.
The present inventions provide an improved turbine assembly and improved method of operating a turbine assembly, and they provide an improved interface between a turbine and equipment to which it may be mounted, such as may be used with an air turbine starter or with other turbine applications. One or more aspects of the inventions can be used to reduce the possibility of loss of lubricating oil after ATS puncture. In one aspect of one of the present inventions, components of conventional turbine assemblies can be replaced with improved components for controlling fluid loss from a turbine when a puncture type failure has occurred.
In accordance with one aspect of one of the present inventions, a gas turbine engine combination, such as a gas turbine jet engine, including a jet engine, gearbox and air turbine starter are configured so that a cover plate for the air turbine starter includes at least one passageway and a valve in the at least one passageway for influencing, regulating or controlling fluid flow between the gearbox and the air turbine starter after failure occurs. In one form of one of the inventions, the valve is a normally open valve which closes when the air pressure differential between the ATS and the gearbox increases more than desired. In another form of one of the present inventions, the air turbine starter includes two normally open valves for regulating the pressure differential between the air turbine starter and the gearbox. Preferably, each opening between the air turbine starter and the gearbox allowing air flow between them includes a regulating element for regulating and even shutting off air flow from the gearbox into the air turbine starter when an excessive pressure drop is sensed from the gearbox to the starter. For example, a ring seal can also be included around the output shaft of the air turbine starter to limit excessive air flow from the gearbox to the starter.
In accordance with another aspect of one of the present inventions, an air turbine starter includes a plate or wall engaging part of a housing on the air turbine starter and a valve. The valve may be a normally open valve and preferably allows free-flow of fluid such as oil and air between the ATS and gearbox under normal conditions and limits or eliminates flow from the gearbox to the starter under failure conditions. In one embodiment, the valve is placed in an opening in the wall, such as the opening that vents the starter gearbox and allows the starter to be serviced with oil. In another embodiment, the valve is placed in a passageway extending through another opening in the wall, such as that used for allowing excess oil to drain from the starter back into the gearbox. In accordance with a further aspect of one of the present inventions, an air turbine starter includes a plate or wall engaging part of the housing on the air turbine starter and a normally open valve. The valve is preferably placed on a portion of the air turbine starter adjacent a gearbox to which the starter is mounted. In one form of the inventions, the valve is placed in an opening that allows excess oil to drain from the starter back into the accessory gearbox. In another form of the inventions, the valve is placed in an opening that vents the starter and gearbox and allows the starter to be serviced with oil. In one form of one of the inventions, the valve includes a plastic stopper, and in another form includes a glass or ceramic stopper. The stopper may be spring biased open. The valve may include a housing having a perforated end wall and/or a perforated side wall.
In another form of one of the present inventions, a kit may be assembled for configuring an air turbine starter to include a valve, wherein the kit includes a cover plate having an opening and a normally open valve for engaging the opening in the cover. In one embodiment, the cover plate includes an engagement surface and the valve includes a complementary engagement surface so that the valve is normally open with a slight pressure differential in the air turbine starter lower than the pressure in the gearbox, and so that the valve is closed when the differential is too high. In one form of the kit, the cover plate includes a ring seal for sealing about an output shaft.
In a further form of one of the present inventions, a method is provided for operating an air turbine starter including allowing air transfer between the air turbine starter and the gearbox. A fluid valve is maintained open under normal operating pressures inside the air turbine housing and closes when the differential pressure between the gearbox and ATS increases above a defined pressure. Such operation may minimize undesirable fluid flow into the air turbine housing, also preferably minimizing the net amount of lubricating oil that flows into the air turbine starter.
These and other features and advantages of the present inventions are set forth in the following detailed description of a preferred embodiments when read in conjunction with the accompanying drawings.